Genetic classification of TTV by digesting the amplified products with endonucleases. Three lanes on the left side schematically represents digestion patterns of the amplified products of G1a, G1b, and G3 subtypes. Three lanes on the right side are photographs of the gel stained with ethidium bromide on which amplified products from UPN 17, 19, and 31 were electrophoresed after digestion with an endonuclease, ScaI, or EcoRI.